[ http://issues.apache.org/jira/browse/DERBY-801?page=all ]
Anders Morken updated DERBY-801:
--------------------------------
Attachment: DERBY-801-v2.patch
DERBY-801-v2.patch is what I've got now. It's not anything very new since the
previous patch, but it's a bit cleaner - and I've spent a lot of time pondering
if what I've done here is safe. I think it mostly is. I'm sorry this has taken
such an awful lot of time - I've been very busy with my day job this summer,
and I haven't really had the time to sit down and do any proper work on this.
Anyway, except for number 2. in my comment above, I think I've mostly addressed
what I worried most about in the last patch. I'd appreciate any comments and
suggestions for further improvement on this one. It passes storeall except for
store/TransactionTable.sql which also fails in a clean trunk checkout. Thanks!
=)
> Allow parallel access to data files.
> ------------------------------------
>
> Key: DERBY-801
> URL: http://issues.apache.org/jira/browse/DERBY-801
> Project: Derby
> Issue Type: Improvement
> Components: Performance, Store
> Affects Versions: 10.0.2.0, 10.0.2.1, 10.1.1.0, 10.1.1.1, 10.1.1.2,
> 10.1.2.0, 10.1.2.1
> Environment: Any
> Reporter: Øystein Grøvlen
> Assigned To: Anders Morken
> Attachments: DERBY-801-v2.patch, NIO-RAFContainer-v1.patch
>
>
> Derby currently serializes accesses to a data file. For example, the
> implementation of RAFContainer.readPage is as follows:
> synchronized (this) { // 'this' is a FileContainer, i.e. a file object
> fileData.seek(pageOffset); // fileData is a RandomAccessFile
> fileData.readFully(pageData, 0, pageSize);
> }
> I have experiemented with a patch where I have introduced several file
> descriptors (RandomAccessFile objects) per RAFContainer. These are
> used for reading. The principle is that when all readers are busy, a
> readPage request will create a new reader. (There is a maximum number
> of readers.) With this patch, throughput was improved by 50% on
> linux. For more discussion on this, see
> http://www.nabble.com/Derby-I-O-issues-during-checkpointing-t473523.html
> The challenge with the suggested approach is to make a mechanism to
> limit the number of open file descpriptors. Mike Matrigali has
> suggested to use the existing CacheManager infrastructure for this
> purpose. For a discussion on that, see:
> http://www.nabble.com/new-uses-for-basic-services-cache---looking-for-advice-t756863.html
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